Many solutions for industrial, medical, or other purposes cannot be readily distinguished by the senses. That is, they may look similar. e.g., colorless or of similar color. and may smell alike, e.g., odorless or having similar odors. For safety and/or hygienic reasons, depending on the nature of the solutions, it may be inconvenient or even dangerous to taste or even touch them.
Various chemical tests are known for identifying or distinguishing among various solutions. These tests generally require that the subject solution be mixed with chemicals or other contaminating substances which render the portion of solution that is tested, thereafter, unusable. Also, chemical tests are generally time consuming, require stocking and restocking of the test chemicals, and necessitate a disposal apparatus for discarding the test solution.